Question Why does my NVIDIA GTX 780 only allow 8 bpc to my ViewSonic VP2770-LED Monitor?

[kaishlothon]

My monitor is a ViewSonic VP2770-LED https://www.tigerdirect.com/applications/searchtools/item-details.asp?EdpNo=4809338&SRCCODE=3WGOOGLEBASE&cm_mmc_o=mH4CjC7BBTkwCjCV1-CjCE&SRCCODE=3WWEBHAN033&gclid=CjwKCAjw8MD7BRArEiwAGZsrBZvVnzJ2QOOWIUUHMbWIVcv7-vJ-aUGSPSv9-fj8LDL-wgZK_PjPJBoCnHoQAvD_BwE and it is powered by an NVIDIA GTX 780 (old as the hills now I know but it used to let me select 10 bpc at 1440p and I could really tell the difference). What might be causing this? (BTW I am using a DisplayPort connection.)